Tuning source for lightwave systems

Abstract

Cost effectiveness and high system reliability are achieved in lightwave systems having at least one tunable sources connected to a network by incorporating a reference signal source within the network useful for tuning at least one tunable source to a predetermined wavelength. The reference signal source generates a signal in a central location within the network and distributes such signal throughout the network. This signal serves as a wavelength reference for tuning the tunable source to a desired wavelength. Transmission of the signal may occur continuously or intermittently. Such a signal may carry one or more wavelengths simultaneously. Alternatively, the reference signal can be generated by wavelength selective reflection of the signal generated by the tunable source.

We claim: 
     
       1. A lightwave system comprising: a lightwave network wherein said network includes an element which supplies a reference signal at a predetermined wavelength; and   a tunable source optically coupled to said network wherein, in response to said reference signal, said tunable source is adjustably controlled to generate a source signal substantially at said predetermined wavelength.   
     
     
       2. The lightwave system of claim 1 wherein said reference signal supplying element comprises wavelength selective reflection responsive to said reference signal. 
     
     
       3. The lightwave system of claim 1 wherein said reference signal supplying element comprises a reference signal generating source. 
     
     
       4. The lightwave system of claim 2 wherein said wavelength selective reflection comprises: a router for receiving said source signal; and   a reflector optically coupled to said router for reflecting a predetermined portion of said source signal wherein said router directs said source signal to said reflector and directs said reflected signal to said tunable source.   
     
     
       5. The lightwave system of claim 2 wherein said reference signal generating source comprises a fiber grating responsive to said source signal for reflecting a portion of said source signal to said tunable source. 
     
     
       6. The lightwave system as in claim 1, wherein said tunable source further comprises a laser for generating said source signal and a control arrangement for adjustably controlling the wavelength of said laser to generate said source signal substantially equal to said predetermined reference wavelength. 
     
     
       7. A lightwave system comprising: a lightwave network wherein said network includes an element which supplies a reference signal at a predetermined wavelength; and   a tunable source comprising a laser source having a gain medium, an optical pump source coupled to said gain medium for inducing population inversion said gain medium, and a locking bandpass filter coupled to said gain medium, wherein said locking bandpass filter is responsive to said reference signal for controlling said tunable source to generate said source signal substantially at said predetermined reference wavelength.   
     
     
       8. A lightwave system comprising: a lightwave network wherein said network includes an element which supplies a reference signal at a predetermined wavelength; and   a tunable source comprising a tunable laser, a locking bandpass filter having a passband coupled to said tunable laser for receiving said reference signal and locking said passband center at said predetermined wavelength, and a control arrangement coupled to said locking bandpass filter generating a control signal to adjustably control the wavelength of said laser to generate a source signal substantially equal to said predetermined wavelength.   
     
     
       9. The lightwave system as in claim 8, wherein said control arrangement includes a detector for detecting intensity of said laser signal and generating a signal relative to said intensity, electrically coupled to a control unit for receiving said detector signal and comparing intensity of said laser signal with that of prior transmission of said laser signal to generate said control signal to adjustably control said laser to generate said source signal at a wavelength exhibiting increased intensity. 
     
     
       10. A lightwave system comprising: a lightwave network wherein said network includes an element which supplies a reference signal at a predetermined wavelength; and   a tunable source comprising a semiconductor laser diode for generating a source signal having a control arrangement for controlling said semiconductor laser diode to generate said source signal at wavelength substantially equal to said predetermined reference wavelength, wherein said control arrangement comprises a locking bandpass filter wherein the center of said filter passband is locked substantially to said predetermined wavelength for controlling said laser diode to generate said source signal.   
     
     
       11. A method of tuning a tunable source in a lightwave system including a network having a reference signal generating source, wherein said reference signal generating source generates a signal at a predetermined wavelength, the method comprising the steps of: transmitting a reference signal from said network to said tunable source; and   adjusting said tunable source to generate a source signal, responsive to said reference signal, at a wavelength substantially equal to said predetermined wavelength.   
     
     
       12. A method of tuning a tunable source which generates a source signal in a lightwave system including a network having wavelength selective reflection of said source signal the method comprising the steps of: reflecting a wavelength selectable portion of said source signal from said tunable source in said network back to said tunable source; and   adjusting said tunable source responsive to said reflected signal to generate a source signal at a wavelength substantially equal to said predetermined wavelength.